R01 title: Nonmydriatic ultra-widefield fundus photography employing trans-pars-planar illumination Summary: This project is to develop a portable pan-retinal imaging device, and validate it for diabetic retinopathy (DR) screening and classification. As a leading cause of blindness, DR is a frequent complication of diabetes mellitus. Prompt screening and early diagnosis is essential to prevent visual impairment and blindness. Emerging widefield fundus photography has demonstrated its superior capability in DR screening, diagnosis and treatment evaluation. However, the high cost and operational complexity of existing widefield fundus imagers limit its potential for telemedicine DR examination, particularly in rural and underserved areas where both expensive instruments and skilled operators are not available. We have recently demonstrated the feasibility of trans-pars- planar illumination, i.e., delivering illuminating light through the pars plana outside of the pupil. By freeing the whole pupil for imaging purpose only, the trans-pars-planar illumination provides a unique opportunity to develop a low-cost, portable, non-mydriatic fundus camera with ultra-widefield coverage. Using all off-the-shelf parts, we have demonstrated a portable, contact-mode fundus camera to cover 200o field of view in a single snapshot image. We propose here to pursue custom-designed optics to develop a portable, eyeball contact-free 230o ultra- widefield fundus camera (u-WFC) to cover the whole retina in a single snapshot image. The first aim of this project is to refine a benchtop prototype WFC to quantitatively characterize optical property of the pars plana. Anticipated outcomes of the aim 1 study are 1) to establish power levels and exposure time required for different pigmentation levels and ages; 2) to establish adjustable distance/angle range of the illuminator; 3) to establish R/G/B ratios required for true color fundus imaging. These numbers will provide all necessary information to detail the system design and specification of the proposed portable u-WFC in Aim 2. The second aim is technical development of a portable u-WFC. The proposed u-WFC can work as either a low-cost handheld device with integrated trans-pars-planar illuminator, or a compact benchtop instrument. Preliminary test of the prototype u- WFC will be conducted using a model eye. FOV, central and peripheral spatial resolutions will be quantified by following the standard procedures defined in ISO 10940:2009. The third aim is clinical validation of the portable u-WFC. DR patients and healthy subjects will be recruited for clinical validation at UIC Retina Clinic. For functional comparison, fundus images will be acquired using the prototype u-WFC, ultra-widefield scanning laser ophthalmoscope (SLO) and OCT angiography (OCTA) at UIC Clinical Research Center of Ophthalmology. Key success criterion of this study is to verify that the portable 230o u-WFC can provide reliable DR detection sensitivity and repeatability, compared to 200o Optos 200Tx (Optos, Marlborough, MA).